Worldbuilding - Mythos

Mythos is a very interesting historical period in many settings because it
defines a lot of interesting societal constructs like religion. In some settings
Mythos might not be viewed as history because the events of mythology have been
disproven, but in others Mythos might be a very real, but perhaps poorly known
period of history.

What distinguishes Mythos from History is how it is recorded. Mythos is often
recorded through oral history, or crude means of recording like cave paintings.
Meaning and details are frequently lost through translation and repetition, so
many of the exact details are lost or subject to multiple versions or interpretations.

Examples

Example 1 - Shadow of Olympus

Again, Greek mythology's creation myth works very well for our Mythos period.
All of the events which took place before humanity's creation fall under the
banner of "Mythos", and what little is known of those events was told to humans
by the gods early in human history, and was passed down for a time through oral
history until humans gained the advantage of written language.

Example 2 - Space Grease

In Space Grease, the Mythos period essentially doesn't exist. Ancient religions
of all kinds have fallen into obscurity as humanity extended its reach to the stars,
and as history became more clearly defined by archaeologists and historians.

Example 3 - Heroes of Tonesvale

Heroes of Tonesvale's mythology is interesting, and we can steal a lot from
comic book superheroes (which I know fairly little about, so bear with me). In
Marvel's universe, the Norse gods exist. They're similar to superpowered humans
from another world with technology so advanced that it is functionally magic.
From the tiny bit of comic book reading I've done, deities from other mythologies
also exist (I know I saw Aries in the New Avengers series when I looked over a
friend's shoulder once).

I like the "all of the above" approach to mythology which Marvel takes. All of
the stories of the ancient mythological gods are told as though they are the only
true story, but they're largely propoganda, superstition, or distortions of the
original facts. The mythological deities all exist, and heroes might draw their
powers from those pantheons.

Just to be safe, I would stay away from pantheons which have already been used
like the Grekoroman and Norse pantheons. More obscure pantheons like pre-European
South American religions would be a great example. Imagine a team of heroes composed
of a robot, a human magician, and the Aztec god of animals or something. I would
read that comic, and I would play that game.